Manufacture of steel



l |II. 1 I I l l Il d l la! l v-lll ATTORNEY Patented July 1'6, 1889.

Fig. 1'.

T. S. BLAIR, Jr. MANUFAUTURE 0F STEEL.

IN. PETERS. Phnxormmgwnef. wmmgm (No Model.)

WTNESSES:

UNITED STATES PATENT OFFICE.

TIIOMASS. BLAIR, J It., OF II'ITSBURG, PENNSYLVANIA.

lVlANUFACTU RE OF STEEL.

SPECIFICATION forming part of Letters Patent No. 407,156, dated July 16, 1889.

Application filed April 22, 1887- Scrial No. 235,747, (No model.)

To all 7071/0712, t may con/ocra.

Be it known that I, THOMAS S. BLAIR, J r., residing at Pittsburg, in the county of Allegheny and State of Pennsylvania, a citizen of the United States, have invented or discovered certain new and useful Improvements in the Manufacture of Steel, of which improvements the following is a specification.

In theaccompanying drawings, which make part of this specification, Figure l is a view, partly in section and part-ly in elevation, of one form of apparatus employed in the practice of my invention. Fig. i is a top plan view of the same.

The invention herein relates to ilnprovements in the open-hearth process of manufacturing steel, whereby I am enabled to produce Iine grades of steel direct from the ore. The open-hearth process, generally stated, consists in dissolving wrought iron or steel scrap in a bath of molten cast-iron, the carbon of the cast-iron disseminating itself with practical uniformity throughout the fluid mass, and the desired degree of carbonization being attained by the due regulation of the proportions of the wrought to the cast iron. In the practice ofv the open-hearth process it is necessary, as above stated, that a portion of charge should be wrought-iron, which is generally produced in a pnddIing-furnace or bloomery-iire; hence the expense and labor incidental to the open-hearth process have been increased in proportion to the amount of wrought-iron enployed.

The object of the invention herein is the manufacture of steel direct from the ore, thereby avoiding the intermediate steps- L'. e., the manufacture of wrought-iron-heretofore necessary; and to this end the invention consists in the method or process substantially as hereinafter more fully described and claimed.

In the practice of my invention the ore to be treated is crushed or broken to a suitable size dependent upon the character of the ore and the carbonaceous material for the deoxidat-ion of the ore mixed therewith in suitable proportions. The amount of carbon-preferably graphitic carbon, which is nearly pure and free from sulphur-used is about twentytive per cent. to thirty-three per cent. of the ore, by weight. The proportions of the ore and carbor will vary, however, in accordance with the character of the ore and carbon. The crushed or broken ore and carbon, being mingled together, are charged into the retorts l, supported upon pillars or posts 2 above the open-hearth furnace 3, of any suitable construction. The retorts arranged in groups or nests Within a shell 4 (see Fig. 2) are provided with doors 5 and G attheir upper and lower ends, (see Fig. 1,) the doors G of the retorts forming one group being preferably connected together so as to be operated simultaneously by a rod 7.4 The upper doors 5 are made suiticiently loose as to permit of the escape of gases or steam from the interior of the retort, and in order to prevent access of air to the ore within the retorts a small amount of carbon is placed on top of the charge. The retorts are heated by the com bustion of gas within the shells 4, the gas from any suitable source being introduced through the pipe S.

Theretorts are maintained at such a heatfi. c., about SOOO Fahrenheit-as will permit the carbon, which has a great afnity for oxygen, to absorb or combine with the oxygen of the ore for a sufficient length of timet. e., about six or eight hours-to effect acom plete deoxidation of the ore, and, as the heat is not sufficient to reduce the oxides-such as phosphoric acid, &c.-to metalloids, thereby produce a practically pure spongy iron. \Vhen a complete reduction has been accomplished, the doors G, at the lower end of the retorts, are opened, thereby permitting the contents of the retorts to drop into 011e of the hoppers 9, leading to an opening in the roof of the furnace 3, said opening being provided with a removable cap or cover 10, which is removed to permit of the passage of the contents ot` the retorts into the hearth. The hoppers 9 are so constructed and arranged in relation to the retorts and the furnace that the spongy iron is protected from the air during its passage to the furnace so as to prevent a reoxidation thereof.

Previous to the discharge of the spongy iron into the open-hearth furnace sufficient pig metal is melted in the furnace to form a bath for dissolving the spongy iron. The

IOO.

u amount of castniron employed as a bath will depend upon the character of spongy iron and other circumstances, Which must be determined by experience; butI ordinarily the proportions of the two metals will be one-third cast-iron and two-thirds spongy iron, or, in other words, only sufcient cast-iron to dissolve or facilitate the melting of the spongy iron is used. If the spongyiron is iinelycomminuted, it should be admitted in comparatively small amounts in order not to clog the furnace; but care should be taken that the deoxidized ore or spongy metal should be discharged into the furnace in such mass or bulk that it will be carried below the surface of the bath, and thereby be protected from the oxidizing heat in the furnace until absorbed or combined with the bath. After the spongy iron has been discharged into the furnace the process is conducted in accordance with the ordinary well-known open-hearth practice, the gangue and oxides of metalloids with which in a mineral state the iron ores are mechanically associated passing off in the slag.

After the spongy iron has been discharged from the retorts the doors 6 are closed, a fresh charge of ore and carbonaceous mate rial is placed in the retorts and reduced, as above described, to spongy iron. This reduction requires approximately the same length of time as the open-hearth process, and hence as soon as the charge previously placed in the furnace has been treated and tapped out and a new bath ofmolten castiron prepared the charge in the retorts will be ready for removal to the furnace, thus forming a continuous as Well as a direct process for the manufacture of steel.

Various attempts have heretofore been made to manufacture steel direct from the ore butwithout any practical success. One of the proposed plans or methods consisted in subjecting the ore to a deoxidizing-flame to reduce it to wrought-iron, then ball and roll such iron, and nally melt and treat it in connection with cast-iron in an open-hearth process. It has also been proposed to deoxidize the ore by packing the same, together with carbonaceous material, in a retort, subjecting the mixed materials to varying degrees of heat, then puddling and rolling, and

nally treating the wrought-iron thus produced in connection with cast-iron in an openhearth furnace in the usual manner. In each of the above-mentioned methods the reduction of the ore to Wrought-iron is an essential preliminary step to the open-hearth processproper; but in my improved process this intermediate step is avoided, the deoxidized ore or iron sponge being charged into a bath of molten cast-iron in the hearth direct from the deoxidizing-retorts.

It has also been proposed to reduce ore to a metallic spongy condition by the combined action of a reducing-gas and carbonaceous material, an d then charge the metallic sponge into a bat-h of molten cast-iron, the cylinder or drum in which such reduction was attempted being in direct and uninterrupted connection with the melting-chamber of the furnace; and hence the action of the reducinggas was impaired or nullitied not only by the oxygen given off by the air, thereby changing the carbonic oxide into carbonio acid-an oxidizing agent;'but the same effect is produced by the oxidizing-gases from the hearth passing through the open passage connecting the hearth and the convertingcylinder. Iron ore has also been reduced to a metallic state by heating it to a greater or less extent in the presence of a carbonaceous material, and after being so reduced has been allowed to cool down and subsequently charged,while in a commin uted condition, into a molten bath.

I claim herein as my invention- The herein-described method of manufacturing steel direet from ore,which consists in heating the ore mixed with carbonaceous material in an air-tight retort for the purpose of deoxidizing the ore, charging the deoxidized ore or spongy iron into a bath of molten cast'- iron directly into the furnace in such masses as will cause the ore or sponge to sink, and finally subjecting the combined metals to the ordinary open-hearth process, substantially as set forth.

In testimony whereof I have hereunto set my hand.

THOMAS S. BLAIR, JR.

NVitnesses:

R. Il. WHITTLESEY, DARWIN S. lVoLcoTT. 

